U.S. patent application number 13/306493 was filed with the patent office on 2012-05-31 for electronic device, electronic apparatus, and method of manufacturing electronic device.
This patent application is currently assigned to SEIKO EPSON CORPORATION. Invention is credited to Yoko KANEMOTO, Ryuji KIHARA.
Application Number | 20120134121 13/306493 |
Document ID | / |
Family ID | 46126539 |
Filed Date | 2012-05-31 |
United States Patent
Application |
20120134121 |
Kind Code |
A1 |
KANEMOTO; Yoko ; et
al. |
May 31, 2012 |
ELECTRONIC DEVICE, ELECTRONIC APPARATUS, AND METHOD OF
MANUFACTURING ELECTRONIC DEVICE
Abstract
An electronic device includes: a vibrator disposed within a
cavity on a substrate and electrically driven; an enclosure wall
which has electric conductivity and sections the cavity from an
insulation layer surrounding the circumference of the cavity; a
first wiring and a second wiring which connect with the vibrator
and penetrate the enclosure wall; and a liquid flow preventing
portion disposed at the position where the first wiring and the
second wiring penetrate the enclosure wall to prevent flow of
etchant dissolving the insulation layer from the cavity toward the
insulation layer and insulate the first wiring and the second
wiring from the enclosure wall.
Inventors: |
KANEMOTO; Yoko; (Fujimi,
JP) ; KIHARA; Ryuji; (Matsumoto, JP) |
Assignee: |
SEIKO EPSON CORPORATION
Tokyo
JP
|
Family ID: |
46126539 |
Appl. No.: |
13/306493 |
Filed: |
November 29, 2011 |
Current U.S.
Class: |
361/748 ;
174/260; 257/E21.158; 29/852 |
Current CPC
Class: |
Y10T 29/49165 20150115;
B81C 2201/053 20130101; B81B 2207/07 20130101; B81B 2201/0271
20130101; B81C 1/00801 20130101 |
Class at
Publication: |
361/748 ;
174/260; 29/852; 257/E21.158 |
International
Class: |
H05K 1/18 20060101
H05K001/18; H05K 3/10 20060101 H05K003/10; H05K 1/16 20060101
H05K001/16 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 2010 |
JP |
2010-266215 |
Claims
1. An electronic device comprising: a function element disposed
within a cavity on a substrate and electrically driven; a covering
portion which has electric conductivity and sections the cavity
from an interlayer insulation film surrounding the circumference of
the cavity; a wiring which connects with the function element and
penetrates the covering portion; and a liquid flow preventing
portion disposed at the position where the wiring penetrates the
covering portion to prevent flow of etchant dissolving the
interlayer insulation film from the cavity toward the interlayer
insulation film and insulate the wiring from the covering
portion.
2. The electronic device according to claim 1, wherein the liquid
flow preventing portion has a corrosion-resistant insulation film
more corrosion-resistant to the etchant than the interlayer
insulation film; and the corrosion-resistant insulation film is
disposed between the wiring and the covering portion.
3. The electronic device according to claim 2, wherein the
interlayer insulation film is made of silicon dioxide; and the
corrosion-resistant insulation film is made of alumina.
4. The electronic device according to claim 1, wherein the liquid
flow preventing portion has a side wall extension which projects
from the covering portion toward the interlayer insulation film;
and the interlayer insulation film is sandwiched between the side
wall extension and the wiring.
5. The electronic device according to claim 4, wherein the
interlayer insulation film sandwiched between the side wall
extension and the wiring has a bending point.
6. An electronic apparatus, comprising: an oscillation circuit,
wherein the oscillation circuit includes the electronic device
according to claim 1.
7. An electronic apparatus, comprising: an oscillation circuit,
wherein the oscillation circuit includes the electronic device
according to claim 2.
8. An electronic apparatus, comprising: an oscillation circuit,
wherein the oscillation circuit includes the electronic device
according to claim 3.
9. An electronic apparatus, comprising: an oscillation circuit,
wherein the oscillation circuit includes the electronic device
according to claim 4.
10. An electronic apparatus, comprising: an oscillation circuit,
wherein the oscillation circuit includes the electronic device
according to claim 5.
11. A method of manufacturing an electronic device, comprising:
forming a wiring connected with a function element provided on a
substrate; forming a corrosion-resistant insulation film covering
the wiring; forming an interlayer insulation film on the substrate,
the wiring, and the corrosion-resistant insulation film; removing
the interlayer insulation film in such a column shape as to
surround the function element, and forming a side wall at the
position from which the interlayer insulation film is removed;
forming a cover having an opening and disposed at a position
overlapping with the side wall and the interlayer insulation film
surrounded by the side wall; forming a protection film on the
interlayer insulation film surrounding the side wall; supplying
etchant through the opening to remove the interlayer insulation
film in the area surrounded by the substrate, the side wall, and
the cover by etching, and to form a cavity; and sealing the
opening, wherein the corrosion-resistant insulation film more
difficult to be etched than the interlayer insulation film is
formed between the wiring and the side wall when the
corrosion-resistant insulation film is formed.
12. A method of manufacturing an electronic device, comprising:
forming a wiring connected with a function element provided on a
substrate; forming an interlayer insulation film covering the
substrate and the wiring; removing the interlayer insulation film
in such a column shape as to surround the function element, and
forming a side wall at the position from which the interlayer
insulation film is removed; forming a side wall extension extended
from the position where the side wall and the wiring cross each
other along the wiring located on the periphery of the side wall;
forming a cover having an opening and disposed at a position
overlapping with the side wall and the interlayer insulation film
surrounded by the side wall; forming a protection film on the
interlayer insulation film surrounding the side wall; supplying
etchant through the opening to remove the interlayer insulation
film in the area surrounded by the substrate, the side wall, and
the cover by etching, and to form a cavity; and sealing the
opening, wherein the wiring is covered by the interlayer insulation
film when the interlayer insulation film is formed, and the
interlayer insulation film covering the wiring is further covered
by the side wall extension when the side wall extension is
formed.
13. The method of manufacturing the electronic device according to
claim 11, wherein an MOS element is provided on the substrate; and
at least one of the wiring and the interlayer insulation film is
formed in a process where the MOS element is formed.
14. An electronic device, comprising: a substrate; a covering
portion disposed on the substrate such that a part of the covering
portion is opposed to another part of the covering portion with a
gap interposed between the opposed parts; an insulation film
disposed on the substrate in such a position as to surround the
covering portion in the plan view as viewed in the substrate
thickness direction; a function element having an electrode and
disposed in a space whose outer periphery is defined by the
substrate and the covering portion; and a wiring disposed on the
substrate and extending between the space and the insulation film
in the plan view as viewed in the substrate thickness direction to
connect with the electrode, wherein the covering portion has a side
wall surrounding the function element in the plan view as viewed in
the substrate thickness direction, and a cover disposed away from
the function element and closing the upper part of the space, and
the side wall has a second insulation film disposed in contact with
the wiring and containing a material different from the material of
the insulation film, and a conductive portion disposed in contact
with the second insulation film.
15. The electronic device according to claim 14, wherein the second
insulation film is made of material which is more etching-resistant
to hydrofluoric acid than the material of the insulation film.
16. An electronic device comprising: a substrate; a covering
portion which is disposed on the substrate such that a part of the
covering portion is opposed to another part of the covering portion
with a gap interposed between the opposed parts, and has electric
conductivity; an insulation film disposed on the substrate in such
a position as to surround the covering portion in the plan view as
viewed in the substrate thickness direction; a function element
having an electrode and disposed in a space whose outer periphery
is defined by the substrate and the covering portion; and a wiring
disposed on the substrate and extending between the space and the
insulation film in the plan view as viewed in the substrate
thickness direction to connect with the electrode, wherein the
covering portion has a side wall surrounding the function element
in the plan view as viewed in the substrate thickness direction,
and a cover disposed away from the function element and closing the
upper part of the space, the side wall at the position where the
wiring penetrates the covering portion has a side wall extension
extending toward the insulation film in the plan view as viewed in
the substrate thickness direction, and the insulation film extends
between the side wall extension and the wiring.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present invention relates to an electronic device, an
electronic apparatus, and a method of manufacturing an electronic
device, and more particularly to an electronic device which has a
cavity.
[0003] 2. Related Art
[0004] An electronic device containing a function element produced
by using MEMS (micro electro mechanical systems) technology is
known, which element is disposed within a cavity on a substrate.
The function element such as a micro vibrator and a micro sensor
has a small structure which vibrates, deforms, or performs other
actions. The pressure within the cavity is reduced so that the
function element can easily operate.
[0005] The method of producing the cavity is disclosed in
JP-A-2009-105411. According to the method shown in this reference,
an interlayer insulation film is initially formed on an MEMS
structure prepared on a substrate. Then, a first covering layer
having through holes is so formed as to cover the interlayer
insulation film around the MEMS structure. After formation of the
first covering layer, etchant is introduced through the through
holes of the first covering layer to remove the interlayer
insulation film and make a movable unit of the MEMS structure
movable. Finally, the through holes of the first covering layer are
covered with a second covering layer so as to produce a closed
cavity around the MEMS structure. The first covering layer is
hereinafter referred to as a covering portion.
[0006] In case of the MEMS structure which is electrically driven,
the covering portion provided thereon is made of material having
electric conductivity so as to prevent entrance of electromagnetic
wave noise into the cavity. In this case, wires connected with the
MEMS structure needs to be insulated from the covering portion so
as to allow extraction of electric signals to the outside of the
covering portion.
[0007] When an interlayer insulation film is disposed between the
wires and the covering portion, this interlayer insulation film is
dissolved by etchant. In this case, the etchant having dissolved
the interlayer insulation film flows toward the area around the
covering portion, which may damage components disposed around the
covering portion. For example, when an interlayer insulation film
is provided around the covering portion, the enchant damages this
interlayer insulation film around the covering portion. As a
result, the strength of the covering portion lowers to such a
degree that the cavity is difficult to be maintained. Accordingly,
such an electronic device which can prevent flow of enchant to the
outside of the covering portion has been demanded.
SUMMARY
[0008] An advantage of some aspects of the invention is to provide
a technology capable of solving at least a part of the
aforementioned problems and the invention can be implemented as the
following forms or application examples.
Application Example 1
[0009] This application example is directed to an electronic device
including: a function element disposed within a cavity on a
substrate and electrically driven; a covering portion which has
electric conductivity and sections the cavity from an interlayer
insulation film surrounding the circumference of the cavity; a
wiring which connects with the function element and penetrates the
covering portion; and a liquid flow preventing portion disposed at
the position where the wiring penetrates the covering portion to
prevent flow of etchant dissolving the interlayer insulation film
from the cavity toward the interlayer insulation film and insulate
the wiring from the covering portion.
[0010] According to the electronic device having this structure,
the interlayer insulation film and the cavity disposed on the
substrate are sectioned from each other via the covering portion.
The function element is provided within the cavity. The wiring is
connected with the function element. The wiring penetrates the
covering portion. The liquid flow preventing portion is provided
between the wiring and the covering portion. The liquid flow
preventing portion insulates the wiring from the covering portion.
Thus, no current flows between the covering portion and the
wiring.
[0011] Etchant dissolves the interlayer insulation film to produce
the cavity within the covering portion. The covering portion is not
easily dissolved by etchant, and thus controls the range of
dissolution by etchant. The wiring provided within the cavity is
not easily dissolved by etchant as well, and is disposed in such a
position as to penetrate the covering portion. When etchant flows
out through the clearance between the wiring and the covering
portion during formation of the cavity, the interlayer insulation
film surrounding the covering portion dissolves. According to the
structure of this application example, the liquid flow preventing
portion is equipped between the wiring and the covering portion.
Thus, flow of etchant out of the covering portion through the
clearance between the wiring and the covering portion can be
prevented by the presence of the liquid flow preventing
portion.
Application Example 2
[0012] This application example is directed to the electronic
device of the above application example, wherein the liquid flow
preventing portion has a corrosion-resistant insulation film more
corrosion-resistant to the etchant than the interlayer insulation
film; and the corrosion-resistant insulation film is disposed
between the wiring and the covering portion.
[0013] According to the electronic device having this structure,
the corrosion-resistant insulation film is provided between the
wiring and the covering portion. The corrosion-resistant insulation
film is more corrosion-resistant to etchant than the interlayer
insulation film. Thus, the corrosion-resistant film insulates the
wiring from the covering portion, and also prevents flow of etchant
out of the covering portion through the clearance between the
wiring and the covering portion.
Application Example 3
[0014] This application example of the invention is directed to the
electronic device of the above application example, wherein the
interlayer insulation film is made of silicon dioxide; and the
corrosion-resistant insulation film is made of alumina.
[0015] According to the electronic device having this structure,
the interlayer insulation film is made of silicon dioxide, and the
corrosion-resistant insulation film is made of alumina. Thus, both
the interlayer insulation film and the corrosion-resistant
insulation film have insulating characteristics. When HF (hydrogen
fluoride) vapor etching is employed for etching, the
corrosion-resistant insulation film securely obtains more
etching-resistant properties than the interlayer insulation
film.
Application Example 4
[0016] This application example of the invention is directed to the
electronic device of the above application example, wherein the
liquid flow preventing portion has a side wall extension which
projects from the covering portion toward the interlayer insulation
film; and the interlayer insulation film is sandwiched between the
side wall extension and the wiring.
[0017] According to the electronic device having this structure,
the liquid flow preventing portion has the side wall extension
projecting from the covering portion toward the interlayer
insulation film. Since the interlayer insulation film is provided
between the side wall extension and the wiring, the side wall
extension is electrically insulated from the wiring. Etchant having
formed the cavity flows from the cavity via the covering portion
toward the interlayer insulation film between the side wall
extension and the wiring, and dissolves the interlayer insulation
film. Generally, the etchant having dissolved the interlayer
insulation film cannot further dissolve the interlayer insulation
film with ease. Thus, the interlayer insulation film disposed in
the area to which the etchant cannot easily flow is difficult to be
dissolved. According to the structure of this application example,
the side wall extension projects, in which arrangement the etchant
having entered between the side wall extension and the wiring
cannot easily flow and thus cannot easily dissolve the interlayer
insulation film. Accordingly, flow of etchant from the cavity
toward the interlayer insulation film can be prevented by the
presence of the side wall extension.
Application Example 5
[0018] This application example of the invention is directed to the
electronic device of the above application example, wherein the
interlayer insulation film sandwiched between the side wall
extension and the wiring has a bending point.
[0019] According to the electronic device having this structure,
the interlayer insulation film covered by the side wall extension
and the wiring has the bending point. The fluid resistance produced
during shift of etchant is higher at the bending point than at a
linear point. In this case, etchant does not easily flow at the
bending point, and therefore the interlayer insulation film
sandwiched between the side wall extension and the wiring is
difficult to be dissolved. Accordingly, flow of etchant from the
cavity toward the interlayer insulation film can be prevented by
the presence of the side wall extension.
Application Example 6
[0020] This application example is directed to an electronic
apparatus including an oscillation circuit. This oscillation
circuit includes the electronic device of the above application
example.
[0021] The electronic apparatus having this structure includes the
oscillation circuit provided with the electronic device described
above as an electronic device producing a waveform. This electronic
device is a high-quality device capable of preventing flow of
etchant from its covering portion. Thus, the electronic apparatus
of this application example becomes an excellent electronic
apparatus equipped with a high-quality electronic device.
Application Example 7
[0022] This application example is directed to a method of
manufacturing an electronic device including: forming a wiring
connected with a function element provided on a substrate; forming
a corrosion-resistant insulation film covering the wiring; forming
an interlayer insulation on the substrate, the wiring, and the
corrosion-resistant insulation film; removing the interlayer
insulation film in such a column shape as to surround the function
element, and forming a side wall at the position from which the
interlayer insulation film is removed; forming a cover having an
opening and disposed at a position overlapping with the side wall
and the interlayer insulation film surrounded by the side wall;
forming a protection film on the interlayer insulation film
surrounding the side wall; supplying etchant through the opening to
remove the interlayer insulation film in the area surrounded by the
substrate, the side wall, and the cover by etching, and to form a
cavity; and sealing the opening. The corrosion-resistant insulation
film more difficult to be etched than the interlayer insulation
film is formed between the wiring and the side wall when the
corrosion-resistant insulation film is formed.
[0023] According to the method of manufacturing the electronic
device of this application example, the wiring connected with the
function element provided on the substrate is formed. The
corrosion-resistant insulation film is formed on the wiring. The
interlayer insulation film is formed on the substrate, the wiring,
and the corrosion-resistant insulation film. The interlayer
insulation film is removed in such a column shape as to surround
the function element, and the side wall is formed at the position
from which the interlayer insulation film is removed. According to
this structure, the interlayer insulation film is positioned in the
area surrounded by the side wall.
[0024] The cover having the opening is formed at the position
overlapped with the side wall and the interlayer insulation film
surrounded by the side wall. The protection film is formed on the
interlayer insulation film surrounding the side wall. According to
this structure, the interlayer insulation film surrounding the side
wall is not etched. The interlayer insulation film provided in the
area surrounded by the side wall and the cover is etched and
removed by etching through the opening to produce the cavity.
Etchant may be introduced through the opening either in spray or in
liquid. The opening is sealed to close the cavity.
[0025] The function element is provided on the substrate. The
wiring is connected with the function element. The
corrosion-resistant insulation film is provided to cover the
wiring. The side wall is provided on the corrosion-resistant
insulation film. In this structure, the wiring is insulated from
the side wall. The corrosion-resistant insulation film is made of a
film more etching-resistant than the interlayer insulation film.
Thus, the corrosion-resistant insulation film remains between the
wiring and the side wall when the interlayer insulation film
surrounded by the side wall is etched. Accordingly, flow of etchant
out of the area surrounded by the side wall through the clearance
between the wiring and the side wall can be prevented.
Application Example 8
[0026] This application example is directed to a method of
manufacturing an electronic device including: forming a wiring
connected with a function element provided on a substrate; forming
an interlayer insulation film covering the substrate and the
wiring; removing the interlayer insulation film in a such a column
shape as to surround the function element, and forming a side wall
at the position from which the interlayer insulation film is
removed; forming a side wall extension extended from the position
where the side wall and the wiring cross each other along the
wiring located on the periphery of the side wall; forming a cover
having an opening and disposed at a position overlapping with the
side wall and the interlayer insulation film surrounded by the side
wall; forming a protection film on the interlayer insulation film
surrounding the side wall; supplying etchant through the opening to
remove the interlayer insulation film in the area surrounded by the
substrate, the side wall, and the cover by etching, and to form a
cavity; and sealing the opening. The wiring is covered by the
interlayer insulation film when the interlayer insulation film is
formed. The interlayer insulation film covering the wiring is
further covered by the side wall extension when the side wall
extension is formed.
[0027] According to the method of manufacturing the electronic
device of the above application example, the wiring connecting with
the function element provided on the substrate is formed. The
interlayer insulation film covering the substrate and the wiring is
formed. The interlayer insulation film provided on the substrate
and the wiring is removed in such a column shape as to surround the
function element. The side wall is formed at the position from
which the interlayer insulation film is removed.
[0028] The interlayer insulation film covering the wiring and
disposed from the position where the side wall and the wiring cross
each other along the wiring on the periphery of the side wall is
further covered by the side wall extension. According to this
structure, the wiring is insulated from the side wall extension.
The cover having the opening is formed at the position overlapping
with the side wall and the interlayer insulation film surrounded by
the side wall. The protection film is formed on the interlayer
insulation film surrounding the side wall. According to this
structure, the interlayer insulation film surrounding the side wall
is not etched. The interlayer insulation film provided in the area
surrounded by the side wall and the cover is etched and removed by
etching through the opening to produce the cavity. The opening is
sealed to close the cavity.
[0029] The function element is provided on the substrate. The
wiring is connected with the function element. The interlayer
insulation film is provided on the wiring. The side wall and the
side wall extension covering the interlayer insulation film are
provided. According to this structure, etchant does not easily flow
out of the area surrounded by the side wall through the clearance
between the wiring and the side wall extension compared with the
structure which does not have the side wall extension. Accordingly,
flow of etchant from the area surrounded by the side wall through
the clearance between the wiring and the side wall extension to the
outside can be prevented.
Application Example 9
[0030] This application example of the invention is directed to the
method of manufacturing the electronic device of the above
application example, wherein an MOS element is provided on the
substrate; and at least one of the wiring and the interlayer
insulation film is formed in a process where the MOS element is
formed.
[0031] According to the method of manufacturing the electronic
device of the above application example, the wiring and the
interlayer insulation film are equipped on the MOS (metal oxide
semiconductor) element. The forming of the wiring on the function
element and the forming of the wiring on the MOS element are
performed in the same process. Moreover, the step for forming the
interlayer insulation film on the function element and the step for
forming the interlayer insulation film on the MOS element are
performed in the same process. Thus, the function element and the
MOS element can be produced with higher productivity than by a
method which forms the function element and the MOS element on the
substrate in separate processes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The invention will be described with reference to the
accompanying drawings, wherein like numbers reference like
elements.
[0033] FIG. 1 is a perspective view illustrating the general
disassembled structure of a resonator according to a first
embodiment.
[0034] FIG. 2A is a cross-sectional view schematically illustrating
the resonator taken along a line A-A' in FIG. 1, and FIG. 2B is a
cross-sectional view schematically illustrating the resonator taken
along a line B-B' in FIG. 1.
[0035] FIG. 3A is a block diagram showing a circuit structure of
the resonator, and FIG. 3B is a flowchart showing a method of
manufacturing the resonator.
[0036] FIGS. 4A through 4E schematically illustrate the method of
manufacturing the resonator.
[0037] FIGS. 5A through 5C schematically illustrate the method of
manufacturing the resonator.
[0038] FIGS. 6A through 6C schematically illustrate the method of
manufacturing the resonator.
[0039] FIGS. 7A through 7C schematically illustrate the method of
manufacturing the resonator.
[0040] FIG. 8 is a perspective view illustrating the general
disassembled structure of a resonator according to a second
embodiment.
[0041] FIG. 9A is a cross-sectional view schematically illustrating
the resonator taken along a line C-C' and a line E-E' in FIG. 8,
FIG. 9B is a cross-sectional view schematically illustrating the
resonator taken along a line D-D' and a line F-F' in FIG. 8, and
FIGS. 9C and 9D are enlarged views illustrating a side wall
extension as a main part.
[0042] FIG. 10 is a flowchart showing a method of manufacturing the
resonator.
[0043] FIGS. 11A through 11F schematically illustrate the method of
manufacturing the resonator.
[0044] FIG. 12 schematically illustrates the structure of an MOS
element included in a driving circuit according to a third
embodiment.
[0045] FIG. 13 is an electrical block diagram showing the structure
of a clock according to a fourth embodiment.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0046] Exemplary embodiments according to the invention are
hereinafter described with reference to the drawings. The scales of
the components shown in the respective figures are varied for each
so that these components can be easily recognized in the
figures.
First Embodiment
[0047] Described in this embodiment are a resonator which has a
vibrator disposed within a cavity to output a waveform of a
predetermined frequency, and a characterized example of a method
for manufacturing this resonator with reference to FIGS. 1 through
7C.
Resonator
[0048] FIG. 1 is a perspective view illustrating the general
disassembled structure of the resonator. FIG. 2A is a
cross-sectional view schematically illustrating the resonator taken
along a line A-A' in FIG. 1. FIG. 2B is a cross-sectional view
illustrating the resonator taken along a line B-B' in FIG. 1.
Initially, the structure of the resonator 1 is explained in
conjunction with FIG. 1 and FIGS. 2A and 2B. The resonator 1 as an
electronic device has a rectangular substrate 2. The longitudinal
direction of the substrate 2 corresponds to an X direction, while
the direction perpendicular to the X direction along the plane of
the substrate 2 corresponds to a Y direction. The thickness
direction of the substrate 2 corresponds to a Z direction. The
material of the substrate 2 is not particularly limited but may be
selected from various types of materials such as a semiconductor
substrate including a silicon substrate, a ceramic substrate, a
glass substrate, a sapphire substrate, and a synthetic resin
substrate. For the substrate 2 on which an integrated circuit
containing a semiconductor is provided, a semiconductor substrate
such as a silicon substrate is used. According to this embodiment,
the substrate 2 is constituted by a silicon substrate, for example.
The thickness of the substrate 2 is not specifically limited. In
this embodiment, this thickness lies in the range from 200 .mu.m to
600 .mu.m, for example.
[0049] A first base layer 3 is provided on the substrate 2. The
first base layer 3 is made of trench insulation layer, a LOCOS
(local oxidation of silicon) insulation layer, or a semi-recessed
LOCOS insulation layer, for example. The first base layer 3
functions as an insulation layer which electrically insulates a
plurality of elements formed on the substrate 2 from one
another.
[0050] A second base layer 4 is provided on a part of the first
base layer 3. The material of the second base layer 4 may be any
materials as long as they are corrosion-resistant to etchant used
for etching silicon dioxide film. For example, the second base
layer 4 may be made of alumina. In this case, the second base layer
4 functions as an etching stopper layer during etching on the
second base layer 4.
[0051] A vibrator 5 as a function element is provided on the second
base layer 4 in the vicinity of the center thereof. The vibrator 5
has a fixed electrode 6 and a movable electrode 7. The fixed
electrode 6 is disposed on the second base layer 4. The movable
electrode 7 has a fixed portion 7a, a movable portion 7b, and a
support portion 7c. The fixed portion 7a is disposed on the second
base layer 4. The movable portion 7b is disposed at a position
opposed to the fixed electrode 6. The support portion 7c is so
disposed as to connect the movable portion 7b and the fixed portion
7a, and support the movable portion 7b. The movable portion 7b has
cantilevered structure supported by the support portion 7c. This
structure allows vibration of the movable portion 7b to change the
distance between the movable portion 7b and the fixed electrode
6.
[0052] A first wiring 8 and a second wiring 9 both functioning as
wires are disposed on the second base layer 4. The first wiring 8
is connected with the fixed electrode 6, while the second wiring 9
is connected with the movable electrode 7. A driving circuit 10 is
provided on the first base layer 3. A first intermediate terminal
11 and a second intermediate terminal 12 are further provided on
the first base layer 3. One end of the first wiring 8 is connected
with the driving circuit 10, while the other end of the first
wiring 8 is connected with the first intermediate terminal 11. One
end of the second wiring 9 is connected with the driving circuit
10, while the other end of the second wiring 9 is connected with
the second intermediate terminal 12. A voltage signal applied to
the vibrator 5 can be detected through detection of voltage between
the first intermediate terminal 11 and the second intermediate
terminal 12.
[0053] The driving circuit 10 includes electric elements such as
transistors and capacitors to output a driving signal to the
vibrator 5. A third intermediate terminal 13, a fourth intermediate
terminal 14, and a fifth intermediate terminal are provided on the
first base layer 3. The third intermediate terminal 13 is connected
with the driving circuit 10 via a wiring 13a, while the fourth
intermediate terminal 14 is connected with the driving circuit 10
via a wiring 14a. Similarly, the fifth intermediate terminal 15 is
connected with the driving circuit 10 via a wiring 15a. The third
intermediate terminal 13 is a terminal for a ground line. The
fourth intermediate terminal 14 is a terminal for power supply. The
fifth intermediate terminal 15 is a terminal for signal output. The
driving circuit 10 is a circuit which produces a voltage signal
having a predetermined frequency, and outputs the voltage signal to
the fifth intermediate terminal 15. In other words, the resonator 1
is an oscillator which has both the vibrator 5 and the driving
circuit 10 disposed on the same substrate 2. The parts of the
resonator 1 other than the driving circuit 10 are collectively
referred to as an oscillation device 1a.
[0054] A first enclosure wall 16 is disposed on the second base
layer 4 on the +Y side of the vibrator 5, and a second enclosure
wall 17 is disposed on the second base layer 4 on the -Y side of
the vibrator 5. One end of the first enclosure wall 16 extends to
the vicinity of the first wiring 8, while the other end of the
first enclosure wall 16 extends to the vicinity of the second
wiring 9. Similarly, one end of the second enclosure wall 17
extends to the vicinity of the first wiring 8, while the other end
of the second enclosure wall 17 extends to the vicinity of the
second wiring 9. A sixth intermediate terminal 18 is provided in
the vicinity of the second enclosure wall 17 and connected
therewith via a wiring 18a.
[0055] A first corrosion-resistant insulation film 19 functioning
as a corrosion-resistant insulation film and as a liquid flow
preventing portion is provided on the +X side of the vibrator 5 in
such a position as to cross over the first wiring 8 and connect the
first enclosure wall 16 and the second enclosure wall 17. More
specifically, the first corrosion-resistant insulation film 19
disposed on the first enclosure wall 16 reaches the upper surface
of the first wiring 8 via the second base layer 4 interposed
between the first enclosure wall 16 and the first wiring 8. The
first corrosion-resistant insulation film 19 positioned on the
first wiring 8 further reaches the upper surface of the second
enclosure wall 17 via the second base layer 4 interposed between
the first wiring 8 and the second enclosure wall 17. The second
base layer 4 is provided on the area surrounded by the first
enclosure wall 16 and the second enclosure wall 17 and the area
surrounding the two enclosure walls 16 and 17. According to this
structure, the area of the substrate 2 surrounded by the first
enclosure wall 16 and the second enclosure wall 17 is covered by
the second base layer 4. A second corrosion-resistant insulation
film 20 functioning as a corrosion-resistant insulation film and as
a liquid flow preventing portion is provided on the -X side of the
vibrator 5 in such a position as to cross over the second wiring 9
and connect the first enclosure wall 16 and the second enclosure
wall 17. The detailed positioning of the second corrosion-resistant
insulation film 20 is similar to that of the first
corrosion-resistant insulation film 19, and the same explanation is
not repeated.
[0056] The vibrator 5, the first wiring 8, the second wiring 9, the
first intermediate terminal 11 through the fifth intermediate
terminal 15, the wiring 13a, the wiring 14a, the wiring 15a, the
first enclosure wall 16, the second enclosure wall 17, the sixth
intermediate terminal 18, and the wiring 18a may be made of any
materials as long as they are electrically conductive and
corrosion-resistant to etchant used for etching silicon dioxide.
For example, these materials may be metal or silicon having
electric conductivity. According to this embodiment,
polycrystalline silicon doped with an impurity such as phosphor and
boron to acquire electric conductivity, or aluminum-copper alloy is
employed, for example.
[0057] The first corrosion-resistant insulation film 19 and the
second corrosion-resistant insulation film 20 may be made of any
materials as long as they have both characteristics of electric
insulation and corrosion resistance to etchant used for silicon
dioxide etching. Preferable examples of these materials include
alumina, Si.sub.3N.sub.4, polyimide resin, acrylic resin, novolak
resin, and diazonaphtoquinone resin. According to this embodiment,
the first and second corrosion-resistant films 19 and 20 are made
of alumina, for example.
[0058] A third enclosure wall 22 is overlapped on the first
enclosure wall 16, the second enclosure wall 17, the first
corrosion-resistant insulation film 19, and the second
corrosion-resistant insulation film 20. A fourth enclosure wall 23
is overlapped on the third enclosure wall 22. A fifth enclosure
wall 24 is overlapped on the fourth enclosure wall 23. Each of the
third enclosure wall 22 through the fifth enclosure wall 24 has a
quadrangular frame shape, and is disposed in such a position as to
surround the vibrator 5. The first enclosure wall 16, the second
enclosure wall 17, the first corrosion-resistant insulation film
19, the second corrosion-resistant insulation film 20, the third
enclosure wall 22, the fourth enclosure wall 23, and the fifth
enclosure wall 24 form an enclosure wall 25 surrounding the
vibrator 5.
[0059] The third enclosure wall 22 through the fifth enclosure wall
24 may be made of any materials as long as they have electric
conductivity and sufficient structural strength, and are
corrosion-resistant to etchant used for etching silicon dioxide.
For example, the materials may be selected from polycrystalline
silicon, metals such as aluminum, copper, tungsten, and titanium,
and alloys of these materials. According to this embodiment,
aluminum-copper alloy is used, for example.
[0060] An insulation layer 29 formed by laminating a first
insulation layer 26, a second insulation layer 27, and a third
insulation layer 28 in this order is disposed around the enclosure
wall 25 to function as an interlayer insulation film. The
insulation layer 29 may be made of any materials as long as they
have electrically insulating characteristics and can be removed by
etchant. For example, the insulation layer 29 is made of silicon
dioxide.
[0061] Each of the first enclosure wall 16, the second enclosure
wall 17, the third enclosure wall 22, the fourth enclosure wall 23,
and the fifth enclosure wall 24 is made of electrically conductive
material and electrically connected with one another. The sixth
intermediate terminal 18 is electrically connected with the second
enclosure wall 17. Thus, each of the first enclosure wall 16, the
second enclosure wall 17, the third enclosure wall 22, the fourth
enclosure wall 23, the fifth enclosure wall 24, and the sixth
intermediate terminal 18 has the same potential. The first wiring 8
is surrounded by the first enclosure wall 16, the second enclosure
wall 17, and the third enclosure wall 22 via the first
corrosion-resistant insulation film 19. Since the first
corrosion-resistant insulation film 19 is made of material having
electrically insulating characteristics, the first wiring 8 is
electrically insulated from the first enclosure wall 16, the second
enclosure wall 17, and the third enclosure wall 22. Similarly, the
second wiring 9 is surrounded by the first enclosure wall 16, the
second enclosure wall 17, and the third enclosure wall 22 via the
second corrosion-resistant insulation film 20. Since the second
corrosion-resistant insulation film 20 is made of material having
electrically insulating characteristics, the second wiring 9 is
electrically insulated from the first enclosure wall 16, the second
enclosure wall 17, and the third enclosure wall 22.
[0062] A first sealing layer 30 functioning as a covering portion
and as a cover is disposed on the enclosure wall 25 in such a
manner as to cover the enclosure wall 25. The first sealing layer
30 has a plurality of through holes 30a as openings. The number and
the size of the through holes 30a are not particularly limited.
According to this embodiment, the sixteen through holes 30a are
formed in the first sealing layer 30, for example. The first
sealing layer 30 may be made of any materials as long as they have
electrical conductivity and sufficient structural strength, and are
corrosion-resistant to etchant used for etching silicon dioxide.
According to this embodiment, the first sealing layer 30 has a
laminating structure formed by laminating a titanium layer, a
titanium nitride layer, an aluminum-copper alloy layer, and a
titanium nitride layer in this order, for example.
[0063] A protection film 31 is overlapped on the outer peripheral
area of the first sealing layer 30 and the third insulation layer
28. The protection film 31 is provided in such a position as not to
close the through holes 30a. The protection film 31 may be made of
any materials as long as they are corrosion-resistant to etchant
used for etching silicon dioxide. Examples of the materials of the
protection film 31 include TEOS (tetraethoxysilane) oxide film, and
silicon nitride. According to this embodiment, the protection film
31 is made of a lamination film formed by laminating TEOS oxide
film and a silicon nitride, for example.
[0064] A second sealing layer 32 is laminated on the first sealing
layer 30. The second sealing layer 32 closes the through holes 30a
of the first sealing layer 30. The second sealing layer 32 may be
made of any materials as long as they can form a film having
sufficient strength for closing the through holes 30a. Examples of
the second sealing layer 32 include metal such as aluminum,
titanium, tungsten, and titanium-nickel alloy. According to this
embodiment, the second sealing layer 32 is made of aluminum, for
example. The thickness of the second sealing layer 32 is not
specifically limited. According to this embodiment, this thickness
is set at about 3 .mu.m, for example.
[0065] The area surrounded by the second base layer 4, the
enclosure wall 25, and the first sealing layer 30 corresponds to a
cavity 33. The enclosure wall 25 and the first sealing layer 30
correspond to a covering portion covering the cavity 33. The
vibrator 5 is disposed within the cavity 33. The atmospheric
pressure of the cavity 33 is reduced so that the movable portion 7b
of the movable electrode 7 can easily vibrate. The first sealing
layer 30 and the second sealing layer 32 function as a sealing
member which seals the cavity 33 under the reduced pressure of the
cavity 33.
[0066] First through electrodes 34 are provided at positions
overlapping with the first intermediate terminal 11, the second
intermediate terminal 12, the third intermediate terminal 13, the
fourth intermediate terminal 14, the fifth intermediate terminal
15, and the sixth intermediate terminal 18. Second through
electrodes 35 are provided at positions overlapping with the first
through electrodes 34. Third through electrodes 36 are further
provided at positions overlapping with the second electrodes 35.
Each of the first through electrodes 34, the second through
electrodes 35, and the third electrodes 36 is an electrode
penetrating the first insulation layer 26, the second insulation
layer 27, and the third insulation layer 28.
[0067] An electrode pad 37 is provided on each of the third through
electrodes 36. The protection film 31 is provided such that each of
the electrode pads 37 is exposed through the protection film 31. A
resin layer 38 is laminated on the protection film 31 and the
second sealing layer 32. The resin layer 38 is not provided above
the electrode pads 37. The preferable materials for the resin layer
38 include polyimide resin, silicon modified polyimide resin, epoxy
resin, silicon modified epoxy resin, BCB (benzocyclobutene), PBO
(polybenzoxazole), and other resins. The thickness of the resin
layer 38 is not particularly limited. It is preferable, however,
that this thickness is 10 .mu.m or larger, for example. The resin
layer 38 having a thickness in this range can absorb stress which
may damage the resonator 1 when the resonator 1 is mounted.
[0068] A wiring 39 extends from the upper surface of each of the
electrode pads 37 to the upper surface of the resin layer 38. The
wirings 39 may be made of any materials as long as they have
electric conductivity. Examples of the material for the wirings 39
include a metal layer formed by laminating a titanium-tungsten
alloy layer and a copper layer in this order, a metal layer having
single-layer structure such as a copper layer, a chrome layer, and
an aluminum layer, or a laminated layer formed by laminating these
metal layers.
[0069] External terminals 40 are provided on the wirings 39. The
external terminals 40 are electrically connected with the wirings
39. The external terminals 40 may be made of any materials as long
as they have electric conductivity, such as various types of
metals. According to this embodiment, the external terminals 40 are
made of solder, for example. Each of the external terminals 40 has
a substantially spherical shape.
[0070] A resist layer 41 is laminated on the wirings 39 and the
resin layer 38. The resist layer 41 is provided such that a part of
each of the external terminals 40 is exposed through the resist
layer 41. The resist layer 41 can prevent oxidation and corrosion
of the wirings 39 so as to avoid failure caused by electrical
conditions.
[0071] According to the resonator 1, the external terminals 40 are
directly provided at positions above the substrate 2 constituted by
a chip-shaped semiconductor substrate, for example, as above. Thus,
the package size of the resonator 1 can be made substantially
equivalent to the size of the semiconductor chip.
[0072] The driving circuit 10 is connected with the fixed electrode
6 via the first wiring 8, and further connected with the movable
electrode 7 via the second wiring 9. When voltage is applied to the
vibrator 5 from the driving circuit 10, static electricity is
generated between the fixed electrode 6 and the movable electrode
7. The movable electrode 7 vibrates with the change of the voltage
applied to the vibrator 5, which varies the electrostatic capacity
between the fixed electrode 6 and the movable electrode 7. The
characteristics of the variations of the electrostatic capacity are
determined by the natural frequency of the movable electrode 7.
Accordingly, a voltage waveform of a particular frequency can be
produced by the use of the vibrator 5.
[0073] Under the reduced pressure of the interior of the cavity 33,
the movable electrode 7 can vibrate more easily than when the
cavity 33 is filled with air. Moreover, both the enclosure wall 25
and the first sealing layer 30 have electric conductivity, and
predetermined voltage is kept applied thereto from the sixth
intermediate terminal 18. Thus, even when electromagnetic waves are
transmitted as noise from the outside of the resonator 1,
transmission of electromagnetic waves can be blocked by the
enclosure wall 25 and the first sealing layer 30. Accordingly, the
effect of the electromagnetic waves as noise imposed on the
vibrator 5 can be reduced.
[0074] FIG. 3A is a block diagram showing the circuit structure of
the resonator. As illustrated in FIG. 3A, the driving circuit 10
included in the resonator 1 has an oscillation circuit 44 and a
waveform producing circuit 45. The oscillation circuit 44 is
connected with the vibrator 5 to function as a circuit for
generating a waveform of a predetermined frequency. The waveform
producing circuit 45 has the function of dividing the waveform
outputted from the oscillation circuit 44 to change the frequency
of the waveform, and the function of changing the shape of the
waveform. For example, the waveform producing circuit 45 outputs
waveforms such as triangular waves, rectangular waves, and pulse
waves. The waveform producing circuit 45 can output a waveform of a
frequency lower than the frequency outputted from the oscillation
circuit 44.
Resonator Manufacturing Method
[0075] The above-mentioned method of manufacturing the resonator 1
is now explained with reference to FIGS. 3B through 7C. FIG. 3B is
a flowchart showing the resonator manufacturing method. FIGS. 4A
through 7C schematically illustrate the resonator manufacturing
method. The methods of manufacturing the driving circuit 10, the
third intermediate terminal 13, the fourth intermediate terminal
14, the fifth intermediate terminal 15, and the wirings 13a, 14a,
and 15a are known methods, and not specifically explained
herein.
[0076] In the flowchart shown in FIG. 3B, step S1 corresponds to a
wiring forming step which forms the vibrator, the wirings, the
intermediate terminals, the first enclosure wall, and the second
enclosure wall on the substrate. After the end of step S1, the flow
proceeds to step S2. Step S2 corresponds to a corrosion-resistant
insulation film forming step which forms the first
corrosion-resistant insulation film and the second
corrosion-resistant insulation film at positions overlapping with
the wirings. After the end of step S2, the flow proceeds to step
S3. Step S3 corresponds to a first interlayer insulation film
forming step which forms the first insulation layer on the
vibrator. After the end of step S3, the flow proceeds to step S4.
Step S4 corresponds to a first side wall forming step which forms
the third enclosure wall. After the end of step S4, the flow
proceeds to step S5.
[0077] Step S5 corresponds to a second interlayer insulation film
forming step which laminates the second insulation layer on the
first insulation layer. After the end of step S5, the flow proceeds
to step S6. Step S6 corresponds to a second side wall forming step
which forms the fourth enclosure wall at a position overlapping
with the third enclosure wall. After the end of step S6, the flow
proceeds to step S7. Step S7 corresponds to a third interlayer
insulation film forming step which laminates the third insulation
layer on the second insulation layer. The first interlayer
insulation film forming step in step S3, the second interlayer
insulation film forming step in step S5, and the third interlayer
insulation film forming step in step S7 constitute an interlayer
insulation film forming process. After the end of step S7, the flow
proceeds to step S8. Step S8 corresponds to a third side wall
forming step which forms the fifth enclosure wall at a position
overlapping with the fourth enclosure wall. The first side wall
forming step in step S4, the second side wall forming step in step
S6, and the third side wall forming step in step S8 constitute a
side wall forming process. After the end of step S8, the flow
proceeds to step S9. Step S9 corresponds to a cover forming step
which laminates the first sealing layer on the position of the
fifth enclosure wall and the area surrounded by the fifth enclosure
wall. After the end of step S9, the flow proceeds to step S10.
[0078] Step S10 corresponds to a protection film forming step which
forms the protection film around the first sealing layer. After the
end of step S10, the flow proceeds to step S11. Step S11
corresponds to a cavity forming step which forms the cavity by
etching the interlayer insulation layer covered by the enclosure
walls and the first sealing layer. After the end of step S11, the
flow proceeds to step S12. Step S12 corresponds to a sealing step
which forms the second sealing layer at a position overlapping with
the first sealing layer to seal the cavity. After the end of step
S12, the flow proceeds to step S13. Step S13 corresponds to a
terminal forming step which forms the external terminals connecting
with the intermediate terminals. After the end of step S13, the
flow proceeds to step S14. Step S14 corresponds to a dicing step
which cuts the mother substrate into chip-shaped pieces. The
resonator manufacturing process is now completed after the end of
step S14.
[0079] The manufacturing method is herein described in more detail
for each step shown in FIG. 3B with reference to FIGS. 4A through
7C. FIGS. 4A through 4C correspond to the wiring forming step in
step S1. As illustrated in FIG. 4A, a mother substrate 46 is
prepared, and the first base layer 3 and the second base layer 4
are provided on the mother substrate 46. The second base layer 4 is
disposed at the position where the enclosure wall 25 is to be
formed. The mother substrate 46 is a silicon wafer, for example,
and has a sufficient width for producing a plurality of resonators
1. Each part divided from the mother substrate 46 corresponds to
the substrate 2. The first base layer 3 is formed by STI (shallow
trench isolation) method, LOCOS method, or other methods. The
second base layer 4 is formed by CVD (chemical vapor deposition),
sputtering, or by other methods.
[0080] Then, the fixed electrode 6 is provided on the second base
layer 4, and the first wiring 8 is provided on the first base layer
3 and the second base layer 4. In this step, the first intermediate
terminal 11 is simultaneously formed. The fixed electrode 6, the
first wiring 8, and the first intermediate terminal 11 are formed
by a film forming process such as CVD and sputtering, and a
patterning process using photolithography technique and etching
technique. After a pattern made of polycrystalline silicon is
formed, the pattern is doped with a predetermined impurity to
acquire electric conductivity. This doping treatment is conducted
by accumulating dopants in a gas such as POCL.sub.3 and BBr.sub.3,
and thermally diffusing the dopants. Then, an insulation film 6a
and an insulation film 8a are provided on the surfaces of the fixed
electrode 6 and the first wiring 8, respectively, by thermal
oxidation of the fixed electrode 6 and the first wiring 8. At this
time, an oxide film is also formed on the first intermediate
terminal 11.
[0081] Subsequently, as illustrated in FIGS. 4B and 4C, the movable
electrode 7, the second wiring 9, the second intermediate terminal
12, the first enclosure wall 16, and the second enclosure wall 17
are provided. In this step, the sixth intermediate terminal 18 is
simultaneously provided. The movable electrode 7, the second wiring
9, the second intermediate terminal 12, the first enclosure wall
16, the second enclosure wall 17, and the sixth intermediate
terminal 18 are formed by methods similar to the methods for
forming the fixed electrode 6 and the first wiring 8, and the same
explanation is not repeated herein. Then, insulation films 7d,9d,
12a, 16a, and 17a are formed on the surfaces of the movable
electrode 7, the second wiring 9, the second intermediate terminal
12, the first enclosure wall 16, and the second enclosure wall 17,
respectively, by thermal oxidation. At this time, an oxide film is
also formed on the sixth intermediate terminal 18.
[0082] Then, the insulation films 6a, 7d, 16a, and 17a are removed
from the areas where the first corrosion-resistant insulation film
19 and the second corrosion-resistant insulation film 20 are to be
formed. For removing the insulation films, a patterning process
using photolithography technique and etching technique is
employed.
[0083] FIGS. 4D and 4E correspond to the corrosion-resistant
insulation film forming step in step S2. As illustrated in FIGS. 4D
and 4E, the first corrosion-resistant insulation film 19 and the
second corrosion-resistant insulation film 20 are so formed as to
extend from the end of the first enclosure wall 16 to the end of
the second enclosure wall 17. The first corrosion-resistant
insulation film 19 covers a part of the upper surface of the first
wiring 8, while the second corrosion-resistant insulation film 20
covers a part of the upper surface of the second wiring 9. The
first corrosion-resistant insulation film 19 and the second
corrosion-resistant insulation film 20 are formed by a film forming
process such as CVD and sputtering, and a patterning process using
photolithography technique and etching technique.
[0084] FIG. 5A corresponds to the first interlayer insulation film
forming step in step S3. As illustrated in FIG. 5A, the first
insulation layer 26 is laminated on the first base layer 3 and the
second base layer 4. In this case, the first insulation layer 26 is
laminated in such a position as to overlap with the first wiring 8,
the second wiring 9, the first corrosion-resistant insulation film
19, and the second corrosion-resistant insulation film 20. The
first insulation layer 26 is formed by a film forming process such
as CVD and sputtering, or a coating method such as spin coating.
After the first insulation layer 26 is formed, a process for
flattening the surface of the first insulation layer 26 may be
performed. The part of the first insulation layer 26 surrounded by
the first enclosure wall 16, the second enclosure wall 17, the
first corrosion-resistant insulation film 19, and the second
corrosion-resistant insulation film 20 corresponds to a first
sacrifice layer 47.
[0085] FIGS. 5B and 5C correspond to the first side wall forming
step in step S4. As illustrated in FIGS. 5B and 5C, the first
insulation layer 26 is patterned. As a result, openings penetrating
the area of the first insulation layer 26 where the third enclosure
wall 22 and the first through electrodes 34 are provided are
formed. The third enclosure wall 22 and the first through
electrodes 34 are produced by embedding metal such as aluminum into
the openings. The third enclosure wall 22 and the first through
electrodes 34 are formed by performing a film forming process such
as CVD and sputtering, and then a patterning process using
photolithography technique and etching technique. The third
enclosure wall 22 and the first through electrodes 34 may be
produced either by the same process or separate processes.
[0086] The third enclosure wall 22 having electric conductivity is
disposed in contact with the first enclosure wall 16 and the second
enclosure wall 17. This arrangement produces continuity across the
first enclosure wall 16 and the second enclosure wall 17 via the
third enclosure wall 22. The first corrosion-resistant insulation
film 19 and the second corrosion-resistant insulation film 20 are
provided between the third enclosure wall 22 and the first wiring 8
and between the third enclosure wall 22 and the second wiring 9,
respectively. Thus, the third enclosure wall 22 is insulated from
both the first wiring 8 and the second wiring 9.
[0087] The first through electrodes 34 are also disposed in contact
with the first intermediate terminal 11, the second intermediate
terminal 12, the third intermediate terminal 13, the fourth
intermediate terminal 14, and the fifth intermediate terminal 15.
This arrangement produces continuity across the first through
electrodes 34 and these terminals.
[0088] FIGS. 6A and 6B correspond to the second interlayer
insulation film forming step in step S5 through the protection film
forming step in step S10. As illustrated in FIG. 6A, the second
interlayer insulation film forming step in step S5 laminates the
second insulation layer 27 on the first insulation layer 26. The
second side wall forming step in step S6 forms openings in the
second insulation layer 27, and then embeds metal such as aluminum
into the openings to produce the fourth enclosure wall 23 and the
second through electrodes 35.
[0089] The third interlayer insulation film forming step in step S7
laminates the third insulation layer 28 on the second insulation
layer 27. The third side wall forming step in step S8 forms
openings in the third insulation layer 28, and then embeds metal
such as aluminum into the openings to produce the fifth enclosure
wall 24 and the third through electrodes 36.
[0090] The area of the second insulation layer 27 surrounded by the
first enclosure wall 16, the second enclosure wall 17, the first
corrosion-resistant insulation film 19, and the second
corrosion-resistant insulation film 20 corresponds to a second
sacrifice layer 49. Similarly, the area of the third insulation
layer 28 surrounded by the first enclosure wall 16, the second
enclosure wall 17, the first corrosion-resistant insulation film
19, and the second corrosion-resistant insulation film 20
corresponds to a third sacrifice layer 50. The first sacrifice
layer 47, the second sacrifice layer 49, and the third sacrifice
layer 50 are collectively referred to as a sacrifice layer 51.
[0091] The second insulation layer 27 and the third insulation
layer 28 are formed by a method similar to the method for forming
the first insulation layer 26, and the same explanation is not
repeated. The fourth enclosure wall 23 and the fifth enclosure wall
24 are formed by a method similar to the method for forming the
third enclosure wall 22, and the same explanation is not repeated.
The second through electrodes 35 and the third through electrodes
36 are formed by a method similar to the method for forming the
first through electrodes 34, and the same explanation is not
repeated.
[0092] The cover forming step in step S9 forms a metal layer 52
produced by laminating a titanium layer, a titanium nitride layer,
an aluminum-copper alloy layer, and a titanium nitride layer in
this order, and laminates the metal layer 52 on the third
insulation layer 28. Subsequently, as illustrated in FIG. 6B, the
metal layer 52 is patterned to produce the first sealing layer 30.
In this step, the through holes 30a are simultaneously formed in
the first sealing layer 30. Then, the metal layer 52 is patterned
to form the electrode pads 37 on the third through electrodes
36.
[0093] The first sealing layer 30 and the electrode pads 37 are
formed by a film forming process such as sputtering and CVD, and
then by a patterning process using photolithography technique and
etching technique, for example. The first sealing layer 30 and the
electrode pads 37 may be produced either by the same process or by
separate processes. The third side wall forming step in step S8 and
the cover forming step in step S9 may be performed by the same
process.
[0094] The protection film forming step in step S10 forms the
protection film 31 on the area of the third insulation layer 28
other than at least a part of the first sealing layer 30. The
protection film 31 is formed by a film forming process such as
sputtering and CVD, and then by a patterning process using
photolithography technique and etching technique, for example.
[0095] FIG. 6C corresponds to the cavity forming step in step S11.
As illustrated in FIG. 6C, the sacrifice layer 51 around the
vibrator 5 is etched through the through holes 30a to form the
cavity 33. HF vapor etching is employed for etching.
[0096] The enclosure wall 25, the first sealing layer 30, and the
protection film 31 are made of corrosion-resistant material to
etchant. Thus, only the sacrifice layer 51 surrounded by the
enclosure wall 25 and the first sealing layer is etched. The
insulation layer 29 surrounding the enclosure wall 25 remains
without being etched.
[0097] The first corrosion-resistant insulation film 19 is provided
between the third enclosure wall 22 and the first wiring 8, between
the first enclosure wall 16 and the first wiring 8, and between the
second enclosure wall 17 and the first wiring 8. This arrangement
prevents leakage of etchant used for etching the sacrifice layer 51
from the enclosure wall 25 along the first wiring 8 toward the
insulation layer 29. Similarly, the second corrosion-resistant
insulation film 20 is provided between the third enclosure wall 22
and the second wiring 9, between the first enclosure wall 16 and
the second wiring 9, and between the second enclosure wall 17 and
the second wiring 9. This arrangement prevents leakage of etchant
used for etching the sacrifice layer 51 from the enclosure wall 25
along the second wiring 9 toward the insulation layer 29.
[0098] FIG. 7A corresponds to the sealing step in step S12. As
illustrated in FIG. 7A, the second sealing layer 32 is provided on
the first sealing layer 30 and the protection film 31. This step
closes the through holes 30a to seal the cavity 33. The second
sealing layer 32 can be formed by a vapor deposition method such as
sputtering and CVD. In this case, the second sealing layer 32 is
produced under reduced pressure. This condition allows the cavity
33 to be sealed while kept under reduced pressure.
[0099] FIGS. 7B and 7C correspond to the terminal forming step in
step S13. As illustrated in FIG. 7B, the resin layer 38 is provided
on the area of the protection film 31 and the second sealing layer
32 other than the upper surfaces of the electrode pads 37. More
specifically, the protection film 31 on the upper surfaces of the
electrode pads 37 is initially opened by patterning which uses
photolithography technique and etching technique. Then, resin is
applied by spin coating, and heat-treated at a temperature
approximately in the range from 300.degree. C. to 400.degree. C. in
an atmosphere of nitrogen. As a result, the applied resin hardens
and forms a film of resin. Finally, the resin film is patterned by
photolithography technique and etching technique to form the resin
layer 38.
[0100] The wirings 39 are provided on the electrode pads 37 and the
resin layer 38. The wirings 39 are formed by a film forming method
such as sputtering and plating, and a patterning method using
photolithography technique and etching technique.
[0101] Then, as illustrated in FIG. 7C, the resist layer 41 is
provided on the resin layer 38 and the wirings 39. The resist layer
41 is formed on the area other than the positions where the
external terminals 40 on the wirings 39 are to be formed. The
resist layer 41 is formed by a film forming process such as spin
coating, and a patterning process using photolithography technique
and etching technique, for example.
[0102] Subsequently, the external terminals 40 are provided on the
wirings 39. The external terminals 40 are produced by forming a
solder film on the wirings 39 and then heating the film at a
temperature approximately in the range from 180.degree. C. to
300.degree. C. to fuse the film.
[0103] In the dicing step in step S14, the mother substrate 46 is
cut along cutting lines. Initially, the mother substrate 46 is
affixed to an adhesive sheet. Then, the mother substrate 46 is cut
along the cutting lines by using a rotary knife the tip of which is
coated with diamond powder. After the cutting, the sheet is spread,
whereby the mother substrate 46 is divided along the cutting lines
into pieces each of which has the size of the substrate 2. As a
result, each of the resonators 1 is separated into a chip shape,
and completed into the form shown in FIG. 1.
[0104] Accordingly, as described above, the following advantages
can be offered in this embodiment.
[0105] (1) According to this embodiment, the cavity 33 is produced
within the enclosure wall 25 when the sacrifice layer 51 is
dissolved by etchant in the cavity forming step in step S11. The
enclosure wall 25 is not easily dissolved by etchant, and therefore
the range to be dissolved by etchant can be defined by the
enclosure wall 25. The first wiring 8 and the second wiring 9
penetrate the enclosure wall 25. When etchant flow out through the
clearances between the first wiring 8 and the enclosure wall 25 and
between the second wiring 9 and the enclosure wall 25 at the time
of formation of the cavity 33, the insulation layer 29 surrounding
the enclosure wall 25 dissolves. According to this embodiment, the
first corrosion-resistant insulation layer 19 and the second
corrosion-resistant insulation layer 20 are provided between the
first wiring 8 and the enclosure wall 25 and between the second
wiring 9 and the enclosure wall 25, respectively. This structure
can prevent flow of etchant from the clearances between the first
wiring 8 and the enclosure wall 25 and between the second wiring 9
and the enclosure wall 25 to the outside of the enclosure wall
25.
[0106] (2) According to this embodiment, the first
corrosion-resistant insulation film 19 and the second
corrosion-resistant insulation film 20 are provided between the
first wiring 8 and the enclosure wall 25 and between the second
wiring 9 and the enclosure wall 25, respectively. The first
corrosion-resistant insulation film 19 and the second
corrosion-resistant insulation film 20 are more corrosion-resistant
to etchant than the sacrifice layer 51. This structure can insulate
the first wiring 8 and the second wiring 9 from the enclosure wall
25, and also can prevent flow of etchant from clearances between
the first wiring 8 and the enclosure wall 25 and between the second
wiring 9 and the enclosure wall 25 to the outside of the enclosure
wall 25.
[0107] (3) According to this embodiment, the sacrifice layer 51 is
made of silicon dioxide, while the first corrosion-resistant
insulation layer 19 and the second corrosion-resistant insulation
film 20 are made of alumina. Thus, the first corrosion-resistant
insulation film 19 and the second corrosion-resistant insulation
film 20 have insulating characteristics. When HF vapor etching is
employed for etching, for example, the first corrosion-resistant
insulation film 19 and the second corrosion-resistant insulation
film 20 become more corrosion-resistant than the sacrifice layer
51.
[0108] (4) According to this embodiment, the resonator 1 has the
vibrator 5 and the oscillation circuit 44 to output the waveform
produced by the oscillation circuit 44. The resonator 1 is a
high-quality electronic device capable of preventing flow of
etchant from the enclosure wall 25. Thus, a high-quality waveform
can be outputted from the resonator 1 as a high-quality electronic
device.
[0109] (5) According to this embodiment, the enclosure wall 25 and
the first sealing layer 30 are formed by conductors. In this case,
transmission of electromagnetic waves to the vibrator 5 can be
blocked by the enclosure wall 25 and the first sealing layer 30 as
conductors whose potentials are fixed by grounding, for example.
Thus, the effect of electromagnetic waves as noise imposed on the
vibrator 5 can be decreased.
[0110] (6) According to this embodiment, the pressure inside the
cavity 33 is reduced. In this condition, the movable electrode 7
more easily vibrates than when the cavity 33 is filled with air.
Thus, the vibrator 5 can vibrate in a high-quality condition.
[0111] (7) According to this embodiment, the enclosure wall 25 is
disposed at the position overlapping with the first
corrosion-resistant insulation film 19 and the second
corrosion-resistant insulation film 20. The first
corrosion-resistant insulation film 19 and the second
corrosion-resistant insulation film 20 are made of alumina. The
enclosure wall 25 is made of aluminum-copper alloy. Thus, these
components 19, 20, and 25 made of metals having similar
coefficients of thermal expansion are not separated from each other
at the time of overheating.
Second Embodiment
[0112] A resonator according to a second embodiment of the
invention is hereinafter described with reference to FIGS. 8
through 11F. This embodiment is different from the first embodiment
in the structure for preventing leakage of etchant. In the
following description, only the different point is touched upon,
and the same explanation is not repeated.
Resonator
[0113] FIG. 8 is a perspective view of the general disassembled
structure of the resonator in this embodiment.
[0114] FIG. 9A is a cross-sectional view schematically illustrating
the resonator taken along a line C-C' and a line E-E' in FIG. 8.
FIG. 9B is a cross-sectional view illustrating the resonator taken
along a line D-D' and a line F-F' in FIG. 8. FIGS. 9C and 9D are
enlarged views illustrating a side wall extension as a main part.
Thus, according to this embodiment, a resonator 55 as an electronic
device includes the vibrator 5, and the driving circuit 10 for
driving the vibrator 5 as illustrated in FIGS. 8 through 9C. The
part of the resonator 55 other than the driving circuit 10 is
referred to as an oscillation device 55a.
[0115] The resonator 55 includes the substrate 2 on which the first
base layer 3 and the second base layer 4 are laminated in this
order. The second base layer 4 may be made of silicon nitride as
well as alumina. The vibrator 5 as a function element is provided
on the second base layer 4 in the vicinity of the center thereof. A
third wiring 56 and a fourth wiring 57 are provided on the second
base layer 4 as wirings. The third wiring 56 is connected with the
fixed electrode 6, while the fourth wiring 57 is connected with the
movable electrode 7.
[0116] A sixth enclosure wall 58 is provided on the second base
layer 4 on the +Y side of the vibrator 5. A seventh enclosure wall
59 is provided on the second base layer 4 on the -Y side of the
vibrator 5. One end of the sixth enclosure wall 58 reaches the
vicinity of the third wiring 56. The other end of the sixth
enclosure wall 58 reaches the vicinity of the fourth wiring 57.
Similarly, one end of the seventh enclosure wall 59 reaches the
vicinity of the third wiring 56. The other end of the seventh
enclosure wall 59 reaches the vicinity of the fourth wiring 57.
[0117] The third wiring 56 extends in the +X direction from the
fixed electrode 6, and has a shape bended at four bending points
56a in the form of a bended line. A first side wall right extension
60 extends in the direction away from the vibrator 5 from a
position where the sixth enclosure wall 58 and the third wiring 56
come close to each other. The first side wall right extension 60 is
provided along the third wiring 56. The clearance between the third
wiring 56 and the first side wall right extension 60 is kept
substantially constant in the area where the third wiring 56 and
the first side wall right extension 60 are disposed adjacent to
each other. Thus, the first side wall right extension 60 extends in
the +X direction from the sixth enclosure wall 58, and has a shape
bended at four bending points 60a in the form of a bended line.
[0118] Similarly, a first side wall left extension 61 extends in
the direction away from the vibrator 5 from a position where the
seventh enclosure wall 59 and the third wiring 56 come close to
each other. The first side wall left extension 61 is provided along
the third wiring 56. The clearance between the third wiring 56 and
the first side wall left extension 61 is kept substantially
constant in the area where the third wiring 56 and the first side
wall left extension 61 are disposed adjacent to each other. Thus,
the first side wall left extension 61 extends in the +X direction
from the sixth enclosure wall 58, and has a shape bended at four
bending points 61a in the form of a bended line.
[0119] The clearance between the first side wall right extension 60
and the third wiring 56 is narrow to such an extent as to avoid
short circuit. Thus, the third wiring 56 is insulated from the
first side wall right extension 60. Similarly, the clearance
between the first side wall left extension 61 and the third wiring
56 is narrow to such an extent as to avoid short circuit. Thus, the
third wiring 56 is insulated from the first side wall left
extension 61.
[0120] The fourth wiring 57 extends in the -X direction from the
movable electrode 7, and has a shape bended at four bending points
57a in the form of a bended line. A second side wall right
extension 62 extends in the direction away from the vibrator 5 from
a position where the sixth enclosure wall 58 and the fourth wiring
57 come close to each other. The second side wall right extension
62 is provided along the fourth wiring 57. The clearance between
the fourth wiring 57 and the second side wall right extension 62 is
kept substantially constant in the area where the fourth wiring 57
and the second side wall right extension 62 are disposed adjacent
to each other. Thus, the second side wall right extension 62
extends in the -X direction from the sixth enclosure wall 58, and
has a shape bended at four bending points 62a in the form of a
bended line.
[0121] Similarly, a second side wall left extension 63 extends in
the direction away from the vibrator 5 from a position where the
seventh enclosure wall 59 and the fourth wiring 57 come close to
each other. The second side wall left extension 63 is provided
along the fourth wiring 57. The clearance between the fourth wiring
57 and the second side wall left extension 63 is kept substantially
constant in the area where the fourth wiring 57 and the second side
wall left extension 63 are disposed adjacent to each other. Thus,
the second side wall left extension 63 extends in the -X direction
from the seventh enclosure wall 59, and has a shape bended at four
bending points 63a in the form of a bended line.
[0122] The clearance between the second side wall right extension
62 and the fourth wiring 57 is narrow to such an extent as to avoid
short circuit. Thus, the fourth wiring 57 is insulated from the
second side wall right extension 62. Similarly, the clearance
between the second side wall left extension 63 and the fourth
wiring 57 is narrow to such an extent as to avoid short circuit.
Thus, the fourth wiring 57 is insulated from the second side wall
left extension 63.
[0123] The sixth enclosure wall 58, the seventh enclosure wall 59,
the first side wall right extension 60, the first side wall left
extension 61, the second side wall right extension 62, and the
second side wall left extension 63 may be made of the same material
as that of the first enclosure wall 16 and the second enclosure
wall 17. Thus, the materials of these components 58 through 63 may
be made of any materials as long as they have electric conductivity
and are corrosion-resistant to etchant used for etching silicon
dioxide. The materials of the components 58 through 63 may be made
of metal or silicon having electric conductivity, for example.
According to this embodiment, polycrystalline silicon doped with
impurity such as phosphor and boron to acquire electric
conductivity is employed, for example.
[0124] A fourth insulation layer 64 functioning as an interlayer
insulation film is provided between the third wiring 56 and the
sixth enclosure wall 58. The fourth insulation layer 64 is also
provided between the third wiring 56 and the first side wall right
extension 60. Similarly, the fourth insulation layer 64 is provided
between the third wiring 56 and the seventh enclosure wall 59. The
fourth insulation layer 64 is also provided between the third
wiring 56 and the first side wall left extension 61. The fourth
insulation layer 64 at bending points 64a between the bending
points 56a and the bending points 60a and between the bending
points 56a and the bending points 61a is also bended in the form of
a bended line. The fourth insulation layer 64 is further provided
on the third wiring 56.
[0125] Similarly, a fifth insulation layer 65 functioning as an
interlayer insulation film is provided between the fourth wiring 57
and the sixth enclosure wall 58. The fifth insulation layer 65 is
also provided between the fourth wiring 57 and the second side wall
right extension 62. Similarly, the fifth insulation layer 65 is
provided between the fourth wiring 57 and the seventh enclosure
wall 59. The fifth insulation layer 65 is also provided between the
fourth wiring 57 and the second side wall left extension 63. The
fifth insulation layers 65 at bending points 65a between the
bending points 57a and the bending points 62a and between the
bending points 57a and the bending points 63a are also bended in
the form of a bended line. The fifth insulation layer 65 is further
provided on the fourth wiring 57.
[0126] The fourth insulation layer 64 and the fifth insulation
layer 65 are connected with the first sacrifice layer 47 and the
first insulation layer 26. The fourth insulation layer 64 and the
fifth insulation layer 65 are made of silicon dioxide which is the
same material as that of the first sacrifice layer 47 and the first
insulation layer 26.
[0127] An eighth enclosure wall 66 functioning as a covering
portion and aside wall is provided on the sixth enclosure wall 58,
the seventh enclosure wall 59, the fourth insulation layer 64, and
the fifth insulation layer 65. The fourth enclosure wall 23 and the
fifth enclosure wall 24 are laminated on the eighth enclosure wall
66. The sixth enclosure wall 58, the seventh enclosure wall 59, the
eighth enclosure wall 66, the fourth enclosure wall 23, and the
fifth enclosure wall 24 constitute an enclosure wall 67 functioning
as a covering portion and a side wall surrounding the vibrator 5.
The eighth enclosure wall 66 is a wall corresponding to the third
enclosure wall 22 in the first embodiment. The enclosure wall 67 is
a wall corresponding to the enclosure wall 25 in the first
embodiment.
[0128] A first side wall upper extension 68 is provided on the
first side wall right extension 60, the first side wall left
extension 61, and the fourth insulation layer 64 between the first
side wall right extension 60 and the first side wall left extension
61. That is, the first side wall upper extension 68 extended
between the first side wall right extension 60 and the first side
wall left extension 61 and supported thereby covers the fourth
insulation layer 64. The first side wall right extension 60, the
first side wall left extension 61, and the first side wall upper
extension 68 constitute a first side wall extension 69 functioning
as a liquid flow preventing portion and a side wall extension.
[0129] Similarly, a second side wall upper extension 70 is provided
on the second side wall right extension 62, the second side wall
left extension 63, and the fifth insulation layer 65 between the
second side wall right extension 62 and the second side wall left
extension 63. That is, the second side wall upper extension 70
extended between the second side wall right extension 62 and the
second side wall left extension 63 and supported thereby covers the
fifth insulation layer 65. The second side wall right extension 62,
the second side wall left extension 63, and the second side wall
upper extension 70 constitute a second side wall extension 71
functioning as a liquid flow preventing portion and a side wall
extension.
[0130] Therefore, the fourth insulation layer 64 is sandwiched
between the third wiring 56 and the first side wall extension 69
projecting from the enclosure wall 67 toward the insulation layer
29 in the +X direction. Similarly, the fifth insulation layer 65 is
sandwiched between the fourth wiring 57 and the second side wall
extension 71 projecting from the enclosure wall 67 toward the
insulation layer 29 in the -X direction.
Resonator Manufacturing Method
[0131] A method of manufacturing the resonator 55 described above
is now explained with reference to FIG. 10 and FIGS. 11A through
11F. FIG. 10 is a flowchart showing the resonator manufacturing
method. FIGS. 11A through 11F schematically illustrate the
resonator manufacturing method.
[0132] As shown in the flowchart in FIG. 10, step S21 corresponds
to a wiring forming step which forms the vibrator, the wirings, the
intermediate terminals, the sixth enclosure wall, and the seventh
enclosure wall on the substrate. After the end of step S21, the
flow proceeds to step S22. Step S22 corresponds to a first
interlayer insulation film forming step which forms the first
insulation layer, the fourth insulation layer, and the fifth
insulation layer. The first interlayer insulation film forming step
in step S22, the second interlayer insulation film forming step in
step S5, and the third interlayer insulation film forming step in
step S7 constitute an interlayer insulation film forming process.
After the end of step S22, the flow proceeds to step S23. Step S23
corresponds to a first side wall forming step which forms the
eighth enclosure wall, the first side wall upper extension, and the
second side wall upper extension. The first side wall forming step
in step S23, the second side wall forming step in step S6, and the
third side wall forming step in step S8 constitute a side wall
forming process. After the end of step S23, the flow proceeds to
step S5. The steps after step S5 are similar to the steps after
step S5 in the first embodiment, and the same explanation is not
repeated. The resonator is completed by these manufacturing
steps.
[0133] The manufacturing method is herein explained in detail for
each step shown in FIG. 10 with reference to FIGS. 11A through 11F.
FIGS. 11A and 11B correspond to the wiring forming step in step
S21. As illustrated in FIG. 11A, the mother substrate 46 is
initially prepared, and the first base layer 3 and the second base
layer 4 are provided on the mother substrate 46. The first base
layer 3 and the second base layer 4 may be formed by a method
similar to the corresponding method in the first embodiment.
[0134] Then, as illustrated in FIG. 11B, the fourth wiring 57, the
sixth enclosure wall 58, and the seventh enclosure wall 59 are
provided on the second base layer 4. In this step, the first side
wall right extension 60, the first side wall left extension 61, the
second side wall right extension 62, and the second side wall left
extension 63 are simultaneously provided. These wirings, enclosure
walls, and extensions are formed by a film forming process such as
CVD and sputtering, and a patterning process using photolithography
technique and etching technique. After a pattern made of
polycrystalline silicon is formed, the pattern is doped with a
predetermined impurity to acquire electric conductivity.
[0135] FIG. 11C corresponds to the first interlayer insulation film
forming step in step S22. As illustrated in FIG. 11C, the first
insulation layer 26 is laminated on the fourth wiring 57, the sixth
enclosure wall 58, and the seventh enclosure wall 59. In this step,
the first insulation layer is also laminated on the third wiring
56. The first insulation layer 26 is formed by a film forming
process such as CVD and sputtering. The area of the first
insulation layer 26 surrounded by the sixth enclosure wall 58 and
the seventh enclosure wall 59 corresponds to the first sacrifice
layer 47. The first insulation layer 26 positioned around the third
wiring 56 corresponds to the fourth insulation layer 64. The first
insulation layer 26 positioned around the fourth wiring 57
corresponds to the fifth insulation layer 65.
[0136] FIGS. 11D through 11F correspond to the first side wall
forming step in step S23. As illustrated in FIG. 11D, the first
insulation layer 26 positioned on the sixth enclosure wall 58 and
the seventh enclosure wall 59 is patterned to produce openings
penetrating the first insulation layer 26. Similarly, the first
insulation layer 26 positioned on the first side wall right
extension 60, the first side wall left extension 61, the second
side wall right extension 62, and the second side wall left
extension 63 is patterned to produce openings penetrating the first
insulation layer 26. The fourth insulation layer 64 and the fifth
insulation layer 65 are left without removal.
[0137] As illustrated in FIGS. 11E and 11F, the eighth enclosure
wall 66 and the second side wall upper extension 70 are formed by
embedding metal such as aluminum into the openings. The first side
wall upper extension 68 is formed by a similar method. This step
produces a structure which covers the fifth insulation layer 65 by
the second side wall extension 71, and covers the fourth insulation
layer 64 by the first side wall extension 69.
[0138] The eighth enclosure wall 66, the first side wall upper
extension 68, and the second side wall upper extension 70 are
formed by a film forming process such as CVD and sputtering, and a
patterning process using photolithography technique and etching
technique.
[0139] The steps from the second interlayer insulation film forming
step in step S5 to the protection film forming step in step S10 as
steps performed subsequently to step S23 are similar to the
corresponding steps in the first embodiment, and the same
explanation is not repeated. The cavity forming step in step S11
etches the sacrifice layer 51 positioned around the vibrator 5
through the through holes 30a provided inside the enclosure wall 67
to produce the cavity 33. The etchant used for etching the
sacrifice layer 51 may be hydrofluoric acid or other etchant
capable of dissolving silicon oxide film.
[0140] The first side wall extension 69 is provided at the position
where the third wiring 56 penetrates the enclosure wall 67. The
first side wall extension 69 and the third wiring 56 are disposed
close to each other to such an extent as to avoid short circuit
therebetween. The fourth insulation layer 64 is provided between
the first side wall extension 69 and the third wiring 56. When the
etchant for etching the sacrifice layer 51 shifts along the third
wiring 56, the etchant dissolves the fourth insulation layer 64.
The etching capability of the etchant decreases in the area where
the etchant does not circulate with the progress of etching. The
etchant cannot easily shift from the clearance between the first
side wall extension 69 and the third wiring 56. Thus, the etchant
having dissolved the fourth insulation layer 64 is difficult to
further dissolve the fourth insulation layer 64. Accordingly, the
etchant cannot easily etch the fourth insulation layer 64 at the
position of the first side wall extension 69, which prevents easy
leakage of the etchant from the enclosure wall 67 toward the
insulation layer 29.
[0141] Similarly, the second side wall extension 71 is provided at
the position where the fourth wiring 57 penetrates the enclosure
wall 67. The second side wall extension 71 has a structure similar
to that of the first side wall extension 69. Thus, the etchant
cannot easily etch the fifth insulation layer 65 at the position of
the second side wall extension 71, which prevents easy leakage of
the etchant from the enclosure wall 67 toward the insulation layer
29.
[0142] The steps after the sealing step in step S12 performed
subsequently to step S11 are similar to the corresponding steps in
the first embodiment, and the same explanation is not repeated. By
these steps, the resonator 55 shown in FIG. 8 is completed.
[0143] Accordingly, as described above, the following advantages
can be offered in this embodiment.
[0144] (1) According to this embodiment, the fourth insulation
layer 64 is provided between the first side wall extension 69 and
the third wiring 56. This structure electrically insulates the
first side extension 69 from the third wiring 56. Similarly, the
fifth insulation layer 65 is provided between the second side wall
extension 71 and the fourth wiring 57. This structure electrically
insulates the second side extension 71 from the fourth wiring 57.
Thus, the enclosure wall 67 can be insulated from the third wiring
56 and the fourth wiring 57.
[0145] (2) According to this embodiment, etchant flowing from the
sacrifice layer 51 side via the enclosure wall 67 dissolves the
fourth insulation layer 64 between the first side wall extension 69
and the third wiring 56. The etchant having dissolved the fourth
insulation layer 64 cannot further dissolve the fourth insulation
layer 64 with ease with the progress of etching. Thus, the fourth
insulation layer 64 is difficult to be dissolved in the area to
which the etchant cannot easily flow. Since the first side wall
extension 69 has a projecting shape, the etchant having flowed into
the space between the first side wall extension wall 69 and the
third wiring 56 cannot easily dissolve the fourth insulation layer
64. Therefore, the first side wall extension 69 can prevent flow of
the etchant from the enclosure wall 67 toward the insulation layer
29. Similarly, the second side wall extension 71 having the same
structure as that of the first side wall extension 69 can prevent
flow of the etchant from the enclosure wall 67 toward the
insulation layer 29.
[0146] (3) According to this embodiment, the fourth insulation
layer 64 sandwiched between the first side wall extension 69 and
the third wiring 56 has the bending points 64a. The fluid
resistance produced during shift of the etchant becomes larger at
the bending points 64a than in the linear area of the fourth
insulation layer 64. In this case, the etchant does not easily flow
at the bending points 64a, and therefore does not easily dissolve
the fourth insulation layer 64. Accordingly, flow of the etchant
from the enclosure wall 67 toward the insulation layer 29 can be
prevented by the presence of the first side wall extension 69. The
second side wall extension 71 has the same structure as that of the
first side wall extension 69. The fifth insulation layer 65 has the
bending points 65a. Thus, flow of the etchant from the enclosure
wall 67 toward the insulation layer 29 can be similarly prevented
by the presence of the second side wall extension 71.
[0147] (4) According to this embodiment, the first side wall right
extension 60, the first side wall left extension 61, the second
side wall right extension 62, and the second side wall left
extension 63 are formed by the method similar to the method for
forming the sixth enclosure wall 58 and the seventh enclosure wall
59. Moreover, since the necessity of forming the first
corrosion-resistant insulation film 19 and the second
corrosion-resistant insulation film 20 required in the first
embodiment is eliminated, the step for forming and patterning the
alumina layer need not be performed. Thus, the productivity of the
manufacture of the resonator 55 improves.
Third Embodiment
[0148] A resonator according to a third embodiment of the invention
is hereinafter described with reference to FIG. 12. This embodiment
is different from the first embodiment in that the step for forming
the vibrator 5 and the enclosure wall 25 is performed
simultaneously with apart of the step for forming the driving
circuit 10. In the following description, only the different point
is touched upon, and the same explanation is not repeated.
[0149] FIG. 12 schematically illustrates the structure of an MOS
element included in the driving circuit. As illustrated in FIG. 12,
the driving circuit 10 has the MOS (metal oxide semiconductor)
element. The substrate 2 is doped to form a source region 74 and a
drain region 75. A gate insulation film 76 is provided between the
source region 74 and the drain region 75. The gate insulation film
76 may be made of any insulating materials. According to this
embodiment, the gate insulation film 76 is made of silicon oxide
film, for example. The gate insulation film 76 may be formed by
silicon thermal oxidation, sputtering, or a vapor deposition method
such as CVD.
[0150] A gate electrode layer 77 is laminated on the gate
insulation film 76. For forming the gate electrode layer 77, a
pattern made of polycrystalline silicon is initially formed, and
doped with a predetermined impurity to obtain electric
conductivity. This process may be carried out in the same step as
the step for forming the second wiring 9, the first enclosure wall
16, and the second enclosure wall 17 of the resonator 1.
[0151] The first insulation layer 26 is provided on the gate
electrode layer 77. The first insulation layer 26 is identical to
the first insulation layer 26 provided around the enclosure wall
25. Thus, the first insulation layer 26 according to the embodiment
can be formed in the same step as the step for forming the first
insulation layer 26 in the first embodiment.
[0152] A source electrode 78 is provided on the source region 74. A
drain electrode 79 is provided on the drain region 75. A gate
electrode 80 is provided on the gate electrode layer 77. For
forming the source electrode 78, the drain electrode 79, and the
gate electrode 80, openings are initially formed in the first
insulation layer 26 by a patterning process using photolithography
technique and etching technique. Then, through electrodes are
produced by embedding metal such as aluminum into the openings. The
through electrodes are formed by a film forming process such as CVD
and sputtering, and a patterning process using photolithography
technique and etching technique.
[0153] A wiring 81 is provided on the first insulation layer 26.
The wiring 81 may be formed by using the method for forming the
first through electrodes 34 in the first embodiment. The second
insulation layer 27, the third insulation layer 28, the protection
film 31, the resin layer 38, and the resist layer 41 are laminated
on the wiring 81. These layers 27, 28, 31, 38, and 41 are the same
layers as those in the first embodiment, and can be formed by the
same processes.
[0154] Accordingly, as described above, the following advantages
can be offered in this embodiment.
[0155] (1) According to this embodiment, the MOS element is
provided with the gate electrode layer 77 and the first insulation
layer 26. The step for forming the second wiring 9 and the step for
forming the gate electrode layer 77 of the MOS element are executed
in the same process. Moreover, the step for forming the first
insulation layer 26, the second insulation layer 27, and the third
insulation layer 28 of the insulation layer 29, and the step for
forming the first insulation layer 26, the second insulation layer
27, and the third insulation layer 28 of the MOS element are
executed in the same process. According to this method, the
productivity of the manufacture of the vibrator 5 and the MOS
element improves compared with the method which separately forms
the vibrator 5 and the MOS element on the substrate 2.
Fourth Embodiment
[0156] A clock is hereinafter described with reference to FIG. 13,
as an example of an electronic apparatus including the resonator
according to a fourth embodiment of the invention. This embodiment
is different from the first embodiment in that the resonator is
incorporated in an electronic apparatus. In the following
description, only the different point is touched upon, and the same
explanation is not repeated.
[0157] FIG. 13 is an electric block diagram showing the structure
of the clock. As shown in FIG. 13, a clock 82 as an electronic
apparatus includes a controller 83. The controller 83 is connected
with the resonator 1. The resonator 1 outputs rectangular-wave
signals of a fixed frequency to the controller 83. The controller
83 has a calculation unit which performs various calculations in
synchronization with the rectangular-wave signals.
[0158] The controller 83 has a display unit 84 and an input unit
85. The display unit 84 is a device on which the calculation unit
of the controller 83 displays calculation results. The display unit
84 is constituted by a liquid crystal display, an organic EL
(electro-luminescence) display, an analog-type display such as hour
and minute hands, for example. The input unit 85 is constituted by
a push-button type switch or a rotary dial, for example.
[0159] The clock 82 has a function of displaying the present time.
For displaying the present time, the operator initially inputs time
to the clock 82 at a predetermined time through the input unit 85.
The controller 83 calculates an elapsed time based on the output
from the resonator 1. Then, the controller 83 adds the elapsed time
starting from the input of the time to the inputted time to
calculate the present time, and outputs the calculated present time
to the display unit 84. The display unit 84 displays the present
time based on the signal received from the controller 83.
[0160] The clock 82 further has a stopwatch function. The operator
inputs a command signal for timer start by pushing a button-type
switch provided on the input unit 85. The controller 83 calculates
an elapse of time based on the output from the resonator 1. Then,
the controller 83 calculates the elapsed time starting from the
input of the signal for timer start, and outputs the calculated
time to the display unit 84. The display unit 84 displays the
elapsed time based on the signal received from the controller
83.
[0161] According to this embodiment, as described above, the
following advantages can be offered in this embodiment.
[0162] (1) According to this embodiment, the clock 82 includes the
resonator 1. The resonator 1 is a high-quality device capable of
preventing leakage of etchant from the enclosure wall 25. Thus, the
clock 82 becomes an excellent apparatus provided with the
high-quality resonator 1.
[0163] It should be noted that the invention is not limited to the
respective embodiments described herein, and therefore various
modifications and changes including the following modified examples
may be made.
Modified Example 1
[0164] According to the first embodiment, the vibrator 5 is
provided as an electrically driven function element disposed in the
cavity 33 formed within the enclosure wall 25. The electrically
driven function element is not limited to the vibrator 5 but may be
other elements such as an acceleration sensor having a weight on
the free end of its beam, a gyro sensor, a quartz resonator, an SAW
(surface acoustic wave) element, and a micro actuator movable by a
comb-like electrode. The function element constituted by these
devices can be driven in a high-quality condition due to their
structure capable of preventing flow of etchant from the enclosure
wall 25.
Modified Example 2
[0165] According to the first embodiment, HF vapor etching is used
for etching the sacrifice layer 51. However, the sacrifice layer 51
may be etched by other methods. For example, the sacrifice layer 51
may be etched by using hydrofluoric acid, buffered hydrofluoric
acid or other chemicals as etchant. In this case, it is preferable
that a corrosion-resistant film to etchant is provided on the
second base layer 4. The corrosion-resistant material to etchant
used for this film is not specifically limited. For example, this
film may be made of SiN, titanium, aluminum, or gold. The presence
of this film allows the sacrifice layer 51 to be removed in a
high-quality condition.
Modified Example 3
[0166] According to the first embodiment, the enclosure wall 25 has
three enclosure walls of the third enclosure wall 22, the fourth
enclosure wall 23, and the fifth enclosure wall 24 disposed on the
first enclosure wall 16 and the second enclosure wall 17. The
insulation layer 29 has three insulation layers of the first
insulation layer 26, the second insulation layer 27, and the third
insulation layer 28. The number of the enclosure walls and the
number of the insulation layers are not specifically limited but
may be 1 or 2 layers, or 4 or a larger number of layers. These
numbers may be determined according to the size of the vibrator 5,
and the factors for the manufacturing steps such that the
large-sized vibrator 5 can be used, and that the degree of freedom
for the design of the steps can be raised.
Modified Example 4
[0167] According to the first embodiment, the planar shape of the
enclosure wall 25 is a quadrangular frame shape as illustrated in
FIG. 1. However, the planar shape of the enclosure wall 25 may be
any shapes as long as they can surround the vibrator, such as
circular, elliptical, and polygonal frame shapes. Thus, the degree
of freedom for positioning the wires, the terminals, and the
driving circuit 10 increases. The modified examples 1 through 4 are
applicable to the second embodiment as well.
Modified Example 5
[0168] While the resonator 1 is used in the fourth embodiment, the
resonator 55 may be employed in place of the resonator 1. In this
case, a waveform of a predetermined frequency can be similarly
produced in a high-quality condition.
Modified Example 6
[0169] While the clock 82 has been discussed as an example of the
electronic apparatus including the resonator 1, the resonator 1 may
be incorporated in various types of electronic apparatuses as well
as the clock 82. For example, the resonator 1 may be employed for a
cellular phone, a personal computer, an electronic dictionary, a
digital camera, a digital sound recording and reproducing device,
or others. Each of these devices including the resonator 1 becomes
an electronic apparatus provided with a high-quality oscillator
capable of outputting a waveform of a predetermined frequency in a
high-quality condition.
Modified Example 7
[0170] According to the third embodiment, apart of the step for
forming the MOS element of the driving circuit 10 and a part of the
step for forming the resonator 1 in the first embodiment are
performed in the same process. However, a part of the step for
forming the MOS element of the driving circuit 10 and a part of the
step for forming the resonator 55 in the second embodiment may be
performed in the same process. More specifically, the step for
forming the fourth wiring 57 and the step for forming the gate
electrode layer 77 of the MOS element may be performed in the same
process. Moreover, the step for forming the first insulation layer
26, the second insulation layer 27, and the third insulation layer
28 of the insulation layer 29, and the step for forming the first
insulation layer 26, the second insulation layer 27, and the third
insulation layer 28 of the MOS element are performed in the same
process. In this case, the vibrator 5 and the MOS element can be
manufactured with higher productivity than that of the vibrator 5
and the MOS element manufactured by the method which executes the
step for forming the vibrator 5 and the step for forming the MOS
element separately.
[0171] The entire disclosure of Japanese Patent Application No.
2010-266215, filed Nov. 30, 2010 is expressly incorporated by
reference herein.
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